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United States Patent |
5,169,170
|
Hayashi
|
December 8, 1992
|
Sandwich type ski
Abstract
In construction of a sandwich type ski including a core and upper and lower
surface guards sandwiching the core, a prismatic reinforcement having high
Young's modulus is present about the bottom middle of the core so that
presence of the reinforcement should resist concave warping of the ski in
the lower sliding surface at load application in use via dispersion of
compression on the boundaries between the core and the reinforcement.
Inventors:
|
Hayashi; Keiichi (Hamamatsu, JP)
|
Assignee:
|
Yamaha Corporation (Hamamatsu, JP)
|
Appl. No.:
|
686678 |
Filed:
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April 17, 1991 |
Foreign Application Priority Data
Current U.S. Class: |
280/610 |
Intern'l Class: |
A63C 005/12 |
Field of Search: |
280/610,601,609,11.12
|
References Cited
U.S. Patent Documents
3199882 | Aug., 1965 | Peillex | 280/610.
|
3415529 | Dec., 1968 | Grill et al. | 280/610.
|
4035000 | Jul., 1977 | Lacroix | 280/610.
|
4094528 | Jun., 1978 | Cluzel | 280/610.
|
4667977 | May., 1987 | Lacroix | 280/610.
|
5005853 | Apr., 1991 | Lampl | 280/610.
|
Foreign Patent Documents |
1283134 | Nov., 1968 | DE | 280/610.
|
Primary Examiner: Marmor; Charles A.
Assistant Examiner: Mar; Michael
Attorney, Agent or Firm: Spensley Horn Jubas & Lubitz
Claims
I claim:
1. A sandwich type ski comprising:
an elongated core defined by two side members,
upper and lower elongated surface guards sandwiching said core, and
an elongated, substantially prismatic reinforcement member having a base
with two inclined sides, the prismatic reinforcement member being embedded
in the elongated core about the middle of the width of said core between
the two side members such that the base of the prismatic reinforcement
member is disposed adjacent the lower elongated surface guard, the
prismatic reinforcement member having a higher Young's modulus than that
of the elongated core.
2. A sandwich type ski as claimed in claim 1 in which the transverse cross
sectional profile reinforcement member is an isosceles triangle.
3. A sandwich type ski as claimed in claim 1 in which each interior angle
between the sides and the base of said reinforcement member is in a range
from 45 to 80 degrees.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a sandwich type ski and a method for
producing the same, and more particularly relates to production of an FRP
sandwich type ski having a core of an enhanced resistance against concave
warping by load application in use.
One typical sandwich type ski is made up of an elongated core sandwiched by
a pair of elongated surface guards made of metal such as Al. Use of an
isotropic material such as Al for the surface guards, however, minimizes
elastic response of the ski, increases its weight and disenables user's
free management in use despite its rather smooth sliding characteristics.
In an attempt to remove these demerits inherent to the metal ski, an FRP
sandwich type ski has been proposed and gained expanded use in which an
elongated core is sandwiched by a pair of elongated surface guards made of
fiber reinforced plastics (generally called FRP).
In use of such an FRP sandwich type ski, load application on the binding
located about the middle of its length tends to develop a warping in the
lower sliding surface of the ski which is concave in the transversal
direction of the ski and such concave warping is generally accompanied
with formation of sharp edges on the lateral sides of the lower sliding
surface. As is well known, presence of such sharp edges on the lower
sliding surface seriously impairs smooth sliding of the ski.
SUMMARY OF THE INVENTION
It is therefore the object of the present invention to minimize concave
curvature in the lower sliding surface by load application in use.
In accordance with one aspect of the present invention, a sandwich type ski
is comprised of a core, upper and lower elongated surface guards
sandwiching the core, and an elongated substantially prismatic
reinforcement arranged about the middle of the width of the core.
In accordance with another aspect of the present invention, a cutout of a
substantially triangular transversal cross section is formed in the bottom
face of an FRP core and an elongated, prismatic reinforcement is inserted
into and fixed to the cutout.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view, partly in section, of one embodiment of the
ski in accordance with the present invention,
FIGS. 2 and 3 are perspective and end views for showing one example of
production of the ski in accordance with the present invention,
FIG. 4 is a graph for showing the process of concave warping of the ski in
accordance with the present invention under load application,
FIGS. 5 and 6 are perspective and end views for showing another example of
production of the ski in accordance with the present invention,
FIGS. 7 and 8 are perspective and end views of for showing a further
example of production of the ski in accordance with the present invention,
FIG. 9 is a transverse cross sectional view of a conventional ski,
FIG. 10 is a side view of a conventional ski under application of a load
during use,
FIGS. 11A to 11C are transverse cross sectional views of conventional skis
of various cross sectional constructions,
FIG. 12 is a perspective view of a simulation of a ski under load
application in use,
FIG. 13 depicts concave warping of a ski under the load application shown
in FIG. 12, and
FIGS. 14A to 14C are graphs for showing the process of concave warping of a
conventional ski under load application.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Before proceeding to the present invention, conventional FRP sandwich type
skis will first be explained in reference to FIGS. 9 to 14C.
The typical transversal construction of a conventional FRP sandwich type
ski is shown in FIG. 9, in which the ski a is made up of a core d and a
pair of FRP surface guards b and c sandwiching the core d. When not used,
the construction takes the form shown with solid lines in the drawing.
When a load F is applied to the binding of the ski a as shown in FIG. 10,
the ski a warps in the longitudinal direction. Concurrently, the ski
develops a concave warping in its lower sliding surface as shown with
chain lines in the drawing. Generally, the core construction shown in FIG.
9 is generally called a "one box type" having only one core piece d, that
shown in FIG. 11A a "two box type" in which two core pieces d1 and d2 are
juxtaposed, and those shown in FIGS. 11B and 11C a "three box type" in
each of which three core pieces d1 to d3 are juxtaposed. One example of
the last one is disclosed in Japanese Patent Publication Sho. 58-54834.
One simulation is given in FIG. 12 regarding development of the above
described concave warping of a ski. This model M is assumed to be 50 mm in
width, 10 mm in thickness and 600 mm in length and to be force deformed
over 30 mm at the middle of the length via assistance of a pair of
supports G. It is also assumed that the deformation is linear in mode.
Under this condition, a compression P1 is generated on the upper surface
whereas a tension P2 is generated on the lower surface of the model M. Its
transversal deformation is observed at a location of 40 mm distant from
the middle. The result is shown in FIG. 13 in which a convex curvature is
developed in the upper surface due to the tension P2 and a concave
curvature in the lower surface due to the compression P1. In this context,
the distance L indicates the maximum depth of concave curvature.
Using an Al model M of 72 GPa Young's modulus (E) and and 0.34 Poisson
index (.sigma.), the maximum depth of curvature L is measured. It is
observed from this simulation that the maximum depth is
8.88.times.10.sup.-2 mm or larger for the one box type shown in FIG. 9,
3.12.times.10.sup.-2 mm or larger for the two box type shown in FIG. 11A,
4.04.times.10.sup.-2 mm or larger for the three box type shown in FIG. 11B
and 3.71.times.10.sup.-2 mm or larger for the three box type shown in FIG.
11C.
The process of deformation, i.e. concave warping, is shown in FIGS. 14A to
14C for the various type of core pieces. Here, the y-ordinate indicates
the local depth of curvature whilst the x-ordinate indicates a location
along the width of the ski.
One embodiment of the sandwich type ski in accordance with the present
invention is shown in FIG. 1 in which the ski 1 includes a core 2
sandwiched by upper and lower FRP surface guards 3 and 4. The upper FRP
surface guard 3 is covered with a top plate 6 whereas the lower FRP
surface guard 4 is covered with a slide plate 8. Lateral sides of the core
2 are covered with side coverings 9. The edges of the ski 1 are fortified
with top and sole edge straps 5 and 7. About the middle of the width is
the core 2 accompanied with an elongated, prismatic reinforcement 21 of
high Young's modulus.
One embodiment of the method for producing such a ski is shown in FIGS. 2
and 3, in which a crude core 200 is made of polyurethane resin of 0.50 to
1.00 GPa Young's modulus. About the middle of the width, the crude core is
provided with a cutout 201 of a triangular transversal cross section
having a bottom interior angle in a range from 45 to 80 degrees. The
cutout 201 divides the crude core 200 into core pieces 202 and 203. An
elongated reinforcement 204 of a high Young's modulus and having a like
triangular transversal cross section is inserted into and bonded to the
cutout 201 as shown in FIG. 3. Preferably, the reinforcement 204 is made
of wood of 10 GPa Young's modulus.
The core pieces 202 and 203 on different sides of the reinforcement 204 are
lower in Young's modulus than the reinforcement 204 and may be different
in Young's modulus from each other.
When the ski is curved in the longitudinal direction due to load
application at use, compression generated on the lower surface (see FIG.
13) is dispersed at the boundaries between the central reinforcement 204
and the sideway core pieces 202 and 203 while suppressing concave warping
of the lower sliding surface in the width direction. Assuming that, in the
simulation shown in FIGS. 12 and 13, aluminum material of 72 GPa Young's
modulus (E) and 0.34 Poisson's ratio index (.sigma.) were used, the depth
of curvature would be 2.64.times.10.sup.-2 mm and its process of concave
warping would be such as shown in FIG. 4. When compared with those shown
in FIGS. 14A to 14C, the extent of concave curvature is apparently
smaller.
Another embodiment of the method for producing the above-described ski is
shown in FIGS. 5 and 6. Like the foregoing example, the crude core 200 is
divided into two core pieces 202 and 203 by a triangular cutout 201. An
FRP sheet 205 is interposed between the core pieces 202, 203 and a
triangular, elongated reinforcement 206 which is made of FRP. The FRP
sheet 206 includes reinforcing fibers impregnated with fluid synthetic
resin. After assembling the components, the assembly is heated under
pressure for hardening of the FRP sheet concurrently with bonding of the
assembled components.
A further embodiment of the method for producing the above-described ski is
shown in FIGS. 7 and 8, in which a crude core core 200 is made up of three
separate core pieces 202, 203 and 206, the last one being triangular in
transversal cross section. Each core pieces are covered with fibrous sheet
207 and impregnated with fluid synthetic resin. The three pieces with the
fibers sheets are assembled together and subjected to heating under
pressure. This assembly may preferably carried out concurrently with
assembling of the ski.
The FRP used for the present invention takes the form of rovings, mats,
plain weave cloths, twill weave cloths, bias weave cloths or combinations
thereof. Some fibers that may be used are glass fibers, carbon fibers,
inorganic fibers in general, high tenacity organic fibers or combinations
thereof. The fibers are impregnated with matrix synthetic resin such as
epoxy resins, unsaturated polyester resin, epoxyacrylate resin,
polyurethane resin, polyethylene resin, polyamide resin and combinations
thereof.
For the sliding plate 8 (see FIG. 1) of the ski is preferably used a
polyethylene sheet of a thickness preferably in a range from 0.5 to 1.5
mm. In addition, edges 5 and 7 of various types and various materials can
be used.
As stated above, presence of the reinforcement 204, 206 resists concave
warping of the ski under a load application in use thanks to dispersion of
compression on the boundaries between the reinforcement and its associated
core pieces.
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